We make every effort to ensure the data presented here is accurate based on the best available information currently on file with DEC. It is therefore subject to change as new information becomes available. We recommend contacting the assigned project staff prior to making decisions based on this information.

Problems/Comments

On July 28, 2008 petroleum contamination, likely from an above ground heating oil tank, was discovered adjacent to a former foundation for a homestead house at the Alaska Zoo. DRO and benzene were above ADEC 18 AAC 75 Soil Cleanup Levels. Soil excavated to 3.5' bgs. All contaminated soil was excavated and trucked off to ASR for thermal treatment. Excavation soil sampling analytical results indicated detections for GRO, DRO, RRO, benzene, toluene, and total xylenes but no soil left in place was above Method 2 Migration to GW cleanup levels. Excavated area was paved over after removal. GW not encountered during remedial activities and was expected to be ~8' bgs at the site. Cleanup complete.

Action Information

Action Date

Action

Description

DEC Staff

8/8/2008

Site Characterization Workplan Approved

Reviewed and approved of the Restoration Science & Engineering (RSE) report "Spill at Alaska Zoo: ADEC Spill Notification and Corrective Action Workplan" dated 7/6/08 received by the Contaminated Sites Program (CSP) on 8/6/08. The report showed that DRO and benzene were detected above cleanup levels to 4,610 mg/kg and 0.033 mg/kg, respectively. GRO, RRO, ethylbenzene, toluene, and total xylenes were also detected but below cleanup levels. The contamination was found during recent excavation work pertaining to a parking lot construction. The report proposed that excavation of the contaminated soil occur this summer, the collection of confirmation samples for DRO and BTEX, and that the contaminated soils will be transported to ASR for thermal treatment. The proposed plan was approved provided that a report of the cleanup work be provided to the Department by December 1, 2008 that includes, but is not limited to, findings, analytical data, interpretation of the data, completed laboratory review checklist(s), copies of photographs of the work, and conclusions/recommendations. This approval also includes approval of transport of excavated contaminated petroleum soil to ASR for thermal treatment and confirmation analysis by DRO and BTEX. The upcoming investigation also needs to address whether contamination has or potentially impacted groundwater. If it appears that groundwater may have been impacted, further assessment and/or cleanup may be required. No Laboratory Data Review Checklist was submitted for the soil sample.

Rich Sundet

8/21/2008

Update or Other Action

Received a letter from Alaska Soil Recycling (ASR) indicating 361.04 tons of petroleum impacted soil was received from this site for processing and acknowledged by Contaminated Sites Program staff. No further remedial action is required by the responsible party for these soils.

Rich Sundet

8/26/2008

Site Added to Database

Site added to the database.

Mitzi Read

8/27/2008

Exposure Tracking Model Ranking

Initial ranking with ETM completed.

Mitzi Read

4/15/2009

Update or Other Action

Reviewed a copy of the Restoration Science & Engineering (RSE) report "Corrective Action Report Monitoriong for the Alaska Zoo located 4731 O'Malley Road in Anchorage, Alaska (ADEC File No. 2100.38.502)" dated 1/6/09 received by the CSP on 1/9/09.
On August 18, 2008, an Alaska Zoo parking lot construction contractor loaded stockpiled contaminated soil into trucks and excavated additional soil from the impacted area as assisted by RSE field personnel. The spill was located in a cut section at the south side of a new parking lot that was under construction. RSE field personnel used a PID to screen the excavation limits and soil stockpile. The stockpile was screened to verify that soil was contaminated and additional surface samples were collected from under the stockpile as it was removed. As the stockpile was loaded for transportation to ASR, the ground surface excavation was extended both vertically and in a radial direction from the source-area until field PID screening was below normal background levels. The excavation was extended to approximately one foot below the subgrade elevation of the future parking lot. Soil was presumed to be hydrocarbon-impacted until PID screening yielded background concentrations at or below 0.2 ppmv.
Based upon the pre-development site survey RSE estimates total excavation depths to range in average depths from 2 to 3.5 feet below original ground surface. As some of the area was excavated and stockpiled prior to discovery and notification of the diesel spill, exact depths below original ground surface could not be recorded by RSE. The excavation area measured approximately 40 by 50 feet implying that the release occurred from a surface spill consistent with the historic presence of an above ground heating oil tank.
An RSE qualified sampler collected six samples and one duplicate sample for laboratory analysis for DRO, RRO, GRO, and BTEX. Based on laboratory results, the only contaminant not detected was ethylbenzene. However, all soil sample results (AKZ-1 through AKZ-7) were below ADEC Method 2 migration to GW soil cleanup levels.
361.04 tons of contaminated soil from the hydrocarbon-impacted area was hauled to ASR's thermal treatment facility in Anchorage.

Bill Petrik

4/17/2009

Exposure Tracking Model Ranking

A new updated ranking with ETM has been completed for source area 75790 Homestead Heating Oil AST.

Bill Petrik

3/3/2010

Exposure Tracking Model Ranking

A new updated ranking with ETM has been completed for source area 75790 Homestead Heating Oil AST.

Bill Petrik

4/27/2010

Exposure Tracking Model Ranking

A new updated ranking with ETM has been completed for source area 75790 Homestead Heating Oil AST. Cleanup Complete.

Bill Petrik

4/28/2010

Cleanup Complete Determination Issued

The CSP granted a Corrective Action Complete Determination with no ICs for the site. On 7/28/08 petroleum contamination, likely from a historic above ground heating oil tank, was discovered adjacent to a former foundation for a homestead house at the Alaska Zoo during excavation work pertaining to parking lot construction. DRO and benzene were detected above the 18 AAC 75.341 Method Two Migration to Groundwater (MTG) cleanup levels to 4,610 mg/kg and 0.033 mg/kg, respectively. GRO, RRO, toluene, ethylbenzene, and total xylenes were also detected but below cleanup levels. Further excavation was expanded laterally in order to excavate more impacted soil. Total depth of the excavation was 3.5’ bgs. 7 confirmation samples from the bottom and sidewalls of the final excavation, including 1 duplicate, were submitted for laboratory analysis for GRO, DRO, RRO, and BTEX on 8/18/08. Based on laboratory results, the only contaminant not detected was ethylbenzene. All detections were well below the MTG soil cleanup levels, most at or near their detection limits. The highest concentrations of detected contaminants based on laboratory analytical results, in mg/kg, were 0.818 GRO, 3.27 DRO, 23.2 RRO, 0.0117 benzene, 0.0309 toluene, and 0.0378 total xylenes. The excavation was backfilled with clean soil. 361.04 tons of contaminated soil from the hydrocarbon-impacted area was hauled to the ASR facility for thermal treatment.

Bill Petrik

8/7/2015

Update or Other Action

This file has been archived to Alaska Archives
Barcode: 896981 Box 415

Susan Carberry

Contaminant Information

Name

Level Description

Media

Comments

DRO

< Method 2 Most Stringent

Soil

Benzene

< Method 2 Most Stringent

Soil

Control Type

Type

Details

No ICs Required

Requirements

Missing Location Data

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